1. Field of the Invention
The present invention relates to image sensing systems. More particularly, the present invention relates to CMOS image sensing systems.
2. Description of the Prior Art and Related Information
Imaging systems are being incorporated into a variety of new products and employed in new applications due in large part to cost reductions associated with improved CMOS (Complimentary Metal Oxide Semiconductor) imaging technology as well as the increased availability of low cost processing power to process the resulting image data. For example, automotive applications employing such CMOS imaging systems have been recently introduced. One such automotive application is a lane tracking and lane departure warning system which images the roadway to detect when the vehicle deviates from a lane and issues a lane departure warning. Other automotive as well as other outdoor imaging system applications have been proposed. Such applications have the potential to expose the imaging system to bright sunlight at a variety of different angles and intensities. Also, automobile applications may be exposed to bright headlights shining directly into the imaging system.
In such outdoor applications, and in particular in an automobile lane tracking application using commercially available CMOS image sensors a distorted image output has been experienced under certain lighting conditions. In particular, an undesirable vertical striping effect has been experienced in the CMOS image sensor output under various combinations of daylight brightness and angle of the sun relative to the image sensor. Such distortions of the image output make it more difficult for the associated image processing system, for example a lane tracking system, to identify the relevant portion of the image and perform the image processing function. This in turn can impact on the reliability of the system which is very significant in many applications including the above-noted lane tracking applications.
Accordingly, the increased use of CMOS imaging systems in outdoor environments has created a need for an improved imaging system which is not susceptible to image distortion due to certain outdoor ambient lighting conditions. There is a further need for such an improved imaging system which is not associated with significantly increased costs or difficulty in manufacturing and assembly.